Safety gas-expulsion device for furnaces



March 12, 1940; 5 s ROBERTS 2,193,697

SAFETY GAS-EXPULSION DEVICE FOR FURNACES Filed July 15, 1938 lyweizlor:

Patented Mar. 12, 1940 I UNITED STATES SAFETY GAS-EXPULSION DEVICE FORFURNACES Samuel s. Roberts, Pittsburgh, Pa.

Application July 15, 1938, Serial No. 219,460

7 Claims.

This invention relates to furnaces and, particularly, to an automaticsafety gas-expulsion device therefor.

'In furnaces, especially of the type used for heating metallic articles,having a forced draft or pressure air burners for firing combustiblegaseous fuels, the gases oftentimes accidentally seep into the forceddraft blast mains, the furnace, or the combustion chamber during thetime the forced draft is shut oflf'and the furnace is not in operation,and explode when the furnace is again put into operation, resulting indamage to the' furnace and a hazard to human life. It is thereforedesirable that any waste gases, or gases that may have le'aked'into thefurnace and its associated parts,.be expelled'therefrom while it not inoperation or, at least, before it is again fired and put into operation.

Accordingto the present invention, there is conveniently positioned,close to the furnace in .the forced draft system, a gas-expulsion devicewhich automatically goes into operation to expel the gases from thefurnace and its associated parts whenever the forced draft is shut offand the furnace is not operating.

It is an object of the present invention to provide an improvedgas-expulsion device which will automatically expel any gases from thefurnace when the furnace is not in operation.

It is another object of the invention to provide an improved automaticgas-expulsion device which is simple and inexpensive in its,construction and operation and one which is dependable and willinsure'the expulsion of any gases from the furnace when not inoperation.

It is a still further object of the invention to provide a gas-expulsiondevice which is adapted to be closed and rendered inoperative bytheaction of the forced draft when the furnace is in operation, andpermitted to open and be in operation when the forced draft is shut offand the furnace is not in operation.

Various other objects and advantages of this invention will be moreapparent in the course of the following specification and will beparticu larly pointed out in the appended claims.

In theaccompanying drawing, there is shown,

for the purpose of illustration, one embodiment whichmy invention mayassume in practice.-

In the drawing: Figure 1 is an elevation showing the location of theimproved safety gas expulsion device -of my invention relative to theblower and furnace;

Figure 2 is an enlarged elevation, partly in section, of my improvedsafety gas expulsion de-s vice; and,

Figure 3 is a section taken on the line III- -III on the end of a shaftof a motort, which is suitably arranged on a platform 1 above the blastor forced draft pipe or conduit of a furnace l. The housing 4 of the fanis connected to the blast or forced draft pipe, preferably bymeans of anelbow connection 9 or any other suitable connecting means. The metalliccylinder 2 preferably has a reduced upper end on which there is mounteda smaller cylinder [0 having a hood. I! arranged on the top and spacedfrom the end thereof.

There is arranged in the cylinder 2 and centrally thereof, a valvecomprising a movable spherical member" l3, preferably a spun brass ballhaving a smaller outer diameter than the inner diameter of the cylinderand a cup-like seat member, also preferably of spun brass, attached tothe inside walls of the cylinder and having an opening therein withwhich the ball is adapted to cooperate. The ball I! has arrangeddiametrically therethrough and secured'thereto an upwardly extendingguide tube l5, preferably of brass, and-on the end thereof there isarranged an upwardly-extending rod l6 which is adapted to extendupwardly through an opening in the hood l2. There is arranged below theball l3, and secured to the inner walls of the cylinder 2, a wire basketI! which is adapted to support the brass ball it. There is also arranged, just below the ball, an actuating member l8, preferably a forkedmember, having one end slidably positioned in the lower end of thetubel5 and the forked end thereof pivotally connected to the end of anactuating switch lever l9 extending through a vertically extending slotinthe side of the cylinder 2 to a switch. 20, preferably of a mercoidtype. There is arranged on, the forked member I! a coil compressionspring 2| which is adapted to cooperate between the forked portion ofthe member II and the bottom of the ball I: to cushion the seating 01the same 'in its downward travel.

It will be understood that the weight of the ball and the partsconnected therewith forces the lever ll downwardly, closing the switch20 to actuate the motor I and the fan 5. There is arranged within thecylinder 2 a tension coil spring 22 connected to the switch lever l9 andto the inner wall of the cylinder 2 which is adapted to force the switchlever l9 upwardly to open the switch when the ball l3 and interconnectedparts are in their top-most position, with the ball seated in the memberI. There is associated with the lever I9, next to the slot in the sideof the cylinder 2 through which the lever l8 extends, a sliding door 23which is adapted to be moved by the switch lever in its movement to keepthe slot in the cylinder closed at all times so as to prevent the escapeof the-air therethrough.

The guide tube It is, of course, arranged centrally of the cylinders 2and I0 and there is positioned in the cylinder l0 guide means, such aspreferably a short piece of brass tubing 24 around 'the tube I5, forguiding the vertical movement of. the tube I! and ball l3. The rod I6 isadapted to extend through the hood I2 so as to indicate, at all times,the position of the ball II in the cylinder 2.

It will be understood that so long as the air pressure in the blast orforced draft pipe of the furnace is normal, as it is supposed to beduring the firing thereof, the device is inactive; but when the pressurein this pipe decreases below a fixed point or upon discontinuing the-forced draft,

that is, when the furnace is not being fired, the device becomes activeautomatically as follows:

The air pressure in the blast or forced draft pipe which is of arelatively higher pressure than that generated by the exhaust fan, liftsthe ball "upwardly to seat it in the member H, closing the outletthrough the cylinder to the atmosphere with the switch lever l9beingmoved simultaneously in an upward direction, to open the switch 20,thereby stopping the motor 6 and exhaust fan 5. When the air pressuredrops below a predetermined point, or the blast or forced draft isdiscontinued during the time the furnace is not in operation, the ball[3 drops, cushioning itself on the coil spring 2|, opening the blastpipe to the atmosphere and forcing the lever l9 downwardly to close theswitch 20, thereby starting the motor 6 and the exhaust fan 5. Theexhaust unit then automatically starts to remove any gases that maycollect in the furnace or its associated connections through gas seepagethat may occur through leaking burners or gas valves or any unburnedgases that may have been left in the furnace when it was shutdown,thereby preventing the building up of any explosive mixture in thefurnace or the parts connected therewith. The exhaust gases are forcedupwardly through the cylinder 2 through the wire basket and thespacebetween the sphericalmember or ball i3 and the inner wall of thecylinder into the atmos phere. It will be understood that the pressurein the forced draft pipe is great enough to raise and other forms may bedevised within the scope of my invention, as defined in the appendedclaims.

'I claim:

1. In combination with a pipe or conduit for supplying a forced draft tofurnaces and the like,

' apparatus including an exhaust fan connected to said forced draftpipe, a vertically disposed hollow cylindrical member open to theatmosphere attached to said fan and extending upwardly therefrom, avalve arranged in said cylindrical member intermediate the lengththereof above member upwardly seating the same in the upper valve seatclosing the cylindrical member when a forced draft is passing throughthe pipe, thereby opening the switch so as to prevent the errhaust fanfrom operating and permitting the spherical member to move downwardlydue to the force of gravity, thereby closing the switch and setting theexhaust fan in operation to expel any gases that may collect in thefurnace and the parts associated therewith therefrom into and throughthe cylindrical member and valve into the atmosphere when a forced draftis not passing through the pipe.

2. In combination with a pipe or conduit for supplying a forced draft tofurnaces and the like, apparatus including a safety gas expulsion deviceconsisting of a vertically arranged hollow cylinder open at its ends, aspherical member arranged in said cylinder, means for supporting andguiding said spherical member therein, a seating member arranged in thecylinder above said spherical member and with which it is adapted tocooperate, an exhaust fan positioned below said spherical member andcommunicating with said cylinder and said pipe, said spherical memberadapted to be forced upwardly into said seating member to close thecylinder by the forced draft passing through the pipe, and meansactuated by said spherical member to set said exhaust fan in operationwhen the spherical member is in its lowermost position and the cylinderis open and the forced draft is not passing therethrough, said exhaustfan expelling any gases from the furnace and the parts'associatedtherewith through said valve and cylinder.

3. In combination with a pipe or conduit for supplying a forced draft toa furnace, apparatus including an exhausting means connected to theforced draft pipe and in communication therewith so as to be effectivewhen in operation to expel gases from the furnace and the parts as-'sociated therewith, and means responsive to a predetermined drop in thepressure of the forced draft forautomatically setting said exhaustingmeans in operation.

, 4. In combination with a pipe or conduit for supplying, a forced draftto furnaces and the like, apparatus including an exhausting meansassociated with said pipe for expelling gases from'the furnace and theparts associated therewith when the furnace and forced draft is not inoperation, means controlled by the forced draft for controlling saidexhausting means, said last mentioned means adapted to be actuated bythe forced draft to control the exhausting means so as to make the sameinoperative when a forced draft is passing through the pipe and adaptedto control the exhausting means so as to make the same operative when aforced draft is not passing therethroughi 5. In combination with a pipeor conduit for supplying a forced draft to furnaces and the like,apparatus including a safety gas expulsion device 'havin'g'an exhaustfan associated therewith which is connected to said forced draft pipe,

means controlled by the forced draft for control-- ling said exhaustfan, said last mentioned means adapted to be actuated by the forceddraft to make the exhaust fan inoperative when a forced draft is passingthrough the pipe and adapted to make the exhaust fan operative when aforced draft is not passing therethrough.

6. In combination with a, pipe or conduit for supplying a forced draftto furnaces and the like, apparatus including a safety gas-expulsiondevice consisting of an exhaust fan," a switch for controlling saidexhaust fan and a valve for controlling said switch, said device beingconstructed and arranged so that the forced draft actuates motion so asto expel any gases that may have: collected in the furnace and the partsassociated therewith therefrom.

7.. In combination .witha pipe or conduit for supplying a forced draftto'a furnace, apparatus including a normally inactive exhaust fanconnected to the forced draft pipe and in communication therewith so .asto be effective when in operation to withdraw gases from the furnace andthe parts associated therewith, an outlet duct associated with said fan,a valve interposed between the exit end of said outlet duct and saidfan, a motor for driving said fan, and a switch for controlling saidmotor, said switch being actuated by the movement of said valve, saidvalve being normally closed when normal pressure is maintained in theforced draft pipe thereby maintaining the switch in an open position andthe 1 fan inoperative and being arranged to close the switch so as toplace the motor and fan in operation when the forced draft pressure inthe pipe drops below, a predetermined point.

SAMUEL S. ROBERTS.

